Search Results (22)

The appearance of spin-induced ferroelectric polarization in the so-called type-II multiferroic materials has received a lot of attention. The nature and mechanisms of such polarization were intensively studied using perovskite rare-earth manganites, RMnO₃, as model systems. Later, multiferroic properties were discovered in some RFeO₃ perovskites and possibly in some RCrO₃ perovskites. However, R₂NiMnO₆ double perovskites have ferromagnetic structures that do not break the inversion symmetry. It was found recently that more complex magnetic structures are realized in A-site-ordered quadruple perovskites, RMn₃Ni₂Mn₂O₁₂. Therefore, they have the potential to be multiferroics. In this work, dielectric properties in magnetic fields up to 9 T were investigated for such perovskites as RMn₃Ni₂Mn₂O₁₂ with R = Ce to Ho and for BiMn₃Ni₂Mn₂O₁₂. The samples with R = Bi, Ce, and Nd showed no dielectric anomalies at all magnetic fields, and the dielectric constant decreases with decreasing temperature. The samples with R = Sm to Ho showed qualitatively different behavior when the dielectric constant started increasing with decreasing temperature below certain temperatures close to the magnetic ordering temperatures, T_N. This difference could suggest different magnetic ground states. The samples with R = Eu, Dy, and Ho still showed no anomalies on the dielectric constant. On the other hand, peaks emerged at T_N on the dielectric constant in the R = Sm sample from about 2 T up to the maximum available field of 9 T. The Gd sample showed peaks on dielectric constant at T_N between about 1 T and 7 T. Transition temperatures increase with increasing magnetic fields for R = Sm and decrease for R = Gd. These findings suggest the presence of magnetic-field-induced multiferroic states in the R = Sm and Gd samples with intermediate ionic radii. Dielectric properties at different magnetic fields are also reported for Lu₂NiMnO₆ for comparison. Full article

EU accession countries, including the Republic of Serbia, are under growing pressure to align their plastic waste management systems with EU environmental directives. Despite this, significant challenges remain, including inadequate infrastructure, a limited recycling capacity, and weak enforcement mechanisms. This study employs life cycle assessment (LCA) to evaluate the environmental impacts of polyethylene terephthalate (PET) packaging waste in Serbia, focusing on three end-of-life scenarios (EoL): landfilling, recycling, and incineration. Using GaBi Professional v6.0 software and the ReCiPe 2016 methodology, the results indicate that mismanaged PET waste contributes notably to terrestrial ecotoxicity (3.69 kg 1.4-DB eq.) and human toxicity (non-cancer) (2.36 kg 1.4-DB eq.). In 2023, 14,967.8 tons of PET were collected by authorized operators; however, unreported quantities likely end up in landfills or the natural environment. Beyond the quantified LCA results, this study highlights microplastic pollution as an emerging environmental concern. It advocates for the development of Serbia-specific characterization factors (CFs) for PET microplastics, incorporating localized fate, exposure, and effect data. Tailored CFs would enhance the precision of impact assessments for Serbian terrestrial ecosystems, contributing to more effective, evidence-based environmental policies. These insights are crucial for supporting Serbia’s transition to sustainable waste management and for meeting EU environmental standards. Full article

The aim of this study was to investigate the possibility of Ag nanoparticle crystallization in B₂O₃–Bi₂O₃ glass using a heat treatment method and to investigate the possible influence of the obtained nanoparticles on the emission intensity of Eu³⁺ ions. Borate–bismuth glasses with different B₂O₃:Bi₂O₃ molar ratios of 50:50, 60:40 and 70:50 with Ag and Eu³⁺ ions were successfully synthesized. The structure of the glasses was studied using XRD and FTIR methods. The XRD results exhibited a characteristic amorphous halo, confirming the absence of long-range order in the samples. The glass transition temperatures of various compositions, required to select the annealing temperature, were measured using DTA analysis. The strong maximum in the UV–Vis spectrum of the sample with the highest Bi₂O₃ content clearly indicated the presence of Ag nanoparticles in the glass. Moreover, a color change was observed for this sample, from slightly yellow to red. The presence of Ag nanoparticles was further confirmed via TEM and XPS studies. However, with a high content of Ag nanoparticles in the matrix, their positive effect on luminescence intensity was not observed. The obtained results show that B₂O₃–Bi₂O₃ glass and glass ceramics, with Ag nanoparticles and rare-earth (Re) ions, could be considered as a new phosphor for light-emitting diodes (LEDs). Full article

This review analyzes TiO₂-based coatings formed by the plasma electrolytic oxidation (PEO) process of titanium for the photocatalytic degradation of methyl orange (MO) under simulated solar irradiation conditions. PEO is recognized as a useful technique for creating oxide coatings on various metals, particularly titanium, to assist in the degradation of organic pollutants. TiO₂-based photocatalysts in the form of coatings are more practical than TiO₂-based photocatalysts in the form of powder because the photocatalyst does not need to be recycled and reused after wastewater degradation treatment, which is an expensive and time-consuming process. In addition, the main advantage of PEO in the synthesis of TiO₂-based photocatalysts is its short processing time (a few minutes), as it excludes the annealing step needed to convert the amorphous TiO₂ into a crystalline phase, a prerequisite for a possible photocatalytic application. Pure TiO₂ coatings formed by PEO have a low photocatalytic efficiency in the degradation of MO, which is due to the rapid recombination of the photo-generated electron/hole pairs. In this review, recent advances in the sensitization of TiO₂ with narrow band gap semiconductors (WO₃, SnO₂, CdS, Sb₂O₃, Bi₂O₃, and Al₂TiO₅), doping with rare earth ions (example Eu³⁺) and transition metals (Mn, Ni, Co, Fe) are summarized as an effective strategy to reduce the recombination of photo-generated electron/hole pairs and to improve the photocatalytic efficiency of TiO₂ coatings. Full article

This study employs the first-principles calculation method based on density functional theory to investigate and analyze the effects of doping various rare earthions on the optical properties of bismuth silicate (Bi₄Si₃O₁₂, BSO) crystals. The results indicate that the electronic structure variations of rare earth ions significantly influence the electronic structure and transition characteristics of BSO crystals, thereby altering their optical properties. Specifically, Tm³⁺ doping notably enhances the polarization capability and infrared responsiveness of BSO crystals, Ho³⁺ doping improves their absorption and scattering abilities in the visible light range, while Eu³⁺ doping enhances their ultraviolet absorption. Overall, Tm³⁺ doping and Ho³⁺ doping exhibit the most prominent effects on the optical performance of BSO crystals, providing theoretical guidance for designing and optimizing BSO crystals with specific optical properties. Full article

Fluorescence-based phosphate sensing using phosphate-sensitive phosphors is a promising approach for in situ monitoring of phosphate pollution in waterways and reservoirs. To date, the most sensitive phosphor developed for this purpose is Tb(cpboda)(DMF)₂, where cpboda = (3,3^′-((5-Carboxy-1,3-phenylene)bis(oxy))dibenzoic acid). In this study, we further improve this sensitivity by replacing the ${\mathrm{Tb}}^{3+}$ ions with ${\mathrm{Eu}}^{3+}$ ions to make Eu(cpboda)(DMF${)}_2$ and find concentration-independent phosphate-sensitivity of 1570 ± 120, which is $\approx 8\times$ more sensitive than the Tb-version. This improvement is attributed to ${\mathrm{Eu}}^{3+}$ having a hypersensitive transition, while ${\mathrm{Tb}}^{3+}$ does not. Additionally, we characterize the phosphor’s optical properties, photodegradation, and water solubility. We find that the phosphor presents challenges with regards to both photodegradation and solubility, as it is found to be poorly soluble in water and is quickly photodegraded under UV radiation $<360$ nm. However, these obstacles can, in theory, be overcome with the use of direct excitation of the ${\mathrm{Eu}}^{3+}$ ions at 394 nm and careful design of an analysis instrument to reduce concentration variations. Full article

A series of new lanthanide(III) coordination polymers with the general formula [Ln(btrm)₂(NO₃)₃]_n, where btrm = bis(1,2,4-triazol-1-yl)methane and Ln = Eu³⁺, Tb³⁺, Sm³⁺, Dy³⁺, Gd³⁺ were synthesized and characterized by IR-spectroscopy, elemental, thermogravimetric, single-crystal, and powder X-ray diffraction analyses. Europium(III), samarium(III), terbium(III), and gadolinium(III) coordination polymers demonstrate thermal stability up to 250 °C, while dysprosium(III) is stable up to 275 °C. According to single-crystal X-ray diffraction analysis, the ligand exhibits a bidentate-bridging coordination mode, forming a polymeric chain of octagonal metallocycles. The photoluminescence of the free ligand in the polycrystalline state is observed in the ultraviolet range with a quantum yield of 13%. The energy transfer from the ligand to the lanthanide ions was not observed for all obtained coordination polymers. However, there are sharp bands of lanthanide(III) ions in the diffuse reflectance and excitation spectra of the obtained compounds. Therefore, Ln(III) luminescence arises, most probably, from the enhancement of f-f transition intensity under the influence of the ligand field and non-centrosymmetric interactions. Full article

The novel red-emitting BaBi_2−xEu_xB₄O₁₀ (x = 0.05, 0.1, 0.2, 0.25, 0.3, 0.4, 0.5, 0.6) phosphors were obtained by a crystallization from a glass. Distribution of the Eu³⁺ ions over cation sites were refined for x = 0.1, 0.3 and 0.4 from single-crystal X-ray diffraction data. Emission and excitation spectra of the Eu³⁺-doped BaBi₂B₄O₁₀ phosphors were investigated for the first time, where it was shown that characteristic lines are attributed to the intraconfigurational 4f-4f transitions. The optimal concentration for the BaBi_2−xEu_xB₄O₁₀ phosphors is x = 0.4, after which a luminescence intensity decreases. The CIE chromaticity coordinates for the BaBi₂B₄O₁₀:Eu³⁺ (x = 0.4) phosphor (0.65, 0.35) are close to the NTSC standard values (0.67, 0.33) for commercial red phosphor. The obtained results show that the BaBi₂B₄O₁₀:Eu³⁺ phosphors are promising candidates for solid state lighting application. Full article

We report a possible coexistence of nontrivial topology and antiferromagnetism in the newly discovered compounds EuCdBi${}_2$, with magnetic Eu layer locating above and below Bi square net. The X-ray diffraction on single crystals and powder indicats that this 112-type material crystalizes in space group of $I4/mmm$, the same as SrMnBi${}_2$ and EuMnBi${}_2$. Our combined measurements of magnetization, electrical transport and specific heat consistently reveal antiferromagnetic (AFM) transition of Eu${}^{2+}$ moments at $T_N$ = 20 K. The Eu moments are not saturated under a field of 7 T at 1.8 K. The anisotropic susceptibility suggests the Eu moments lie in the $ab$ plane, and a metamagnetic (MM) transition is observed near 1 T below $T_N$. Large positive magnetoresistance (MR) present for both $H\Vert ab$ and $H\Vert c$, which are considered to contain part contributions from Dirac bands. Hall measurements show the electron-hole compensation effect is prominent above 100 K, with a crossover of Hall resistance from negative to positive values at ∼150 K. The fitted mobility of electrons is as high as 3250 cm${}^2$ V${}^{-1}$ S${}^{-1}$ at 1.8 K. Interestingly, the rapid increase of carrier density and suppression of mobility appear at around $T_N$, indicating non-negligible interaction between Eu moments and electron/hole bands. EuCdBi${}_2$ may provide a new platform to investigate the interplay of topological bands and antiferromagnetic order. Full article

The spectroscopic properties of Eu³⁺-doped Bi₁₂SiO₂₀ (BSO) were investigated and compared with that of Eu³⁺-doped Bi₁₂GeO₂₀ (BGO). The emission properties and the absorption spectra have been measured at 10 K as well as at 300 K (room temperature). Luminescence was detected due to the direct excitation of the ⁵D₀ level of Eu³⁺, as well as through the excitation of the ⁵D₁ level. The Judd–Ofelt theoretical framework was used to compute the radiative lifetimes (τ) and the omega parameters (Ω_λ). The electric dipole transition probabilities, asymmetry ratios (R), along with the branching ratios (β) were also determined based on the obtained experimental data. The strongest detected luminescence belongs to the ⁵D₀ → ⁷F₀ transition observed at 578 nm, similar to the BGO sillenite. Reasons for the major presence of the ⁵D₀ → ⁷F₀ emission, theoretically forbidden by the Judd–Ofelt Theory, were investigated and compared with that of the BGO sillenite. Obtained results showed that the strong ⁵D₀ → ⁷F₀ line is also present in Eu:BSO, indicating that this is a feature of the entire sillenite family and not just Eu:BGO. Full article

There is a growing interest in alternatives to lanthanide ion (Ln(III))-based luminescence sensitizing chromophores for in vivo applications, mainly in optical biological windows. Transition metals (M) are relevant candidates as chromophores as they have high absorption rates and emission bands covering a wide range of visible to near-infrared spectrum. However, despite the importance of theoretical models for the design of M–Ln(III) complexes, few contributions have devoted efforts to elucidating the energy transfer (ET) processes between M and Ln(III) ions. In this context, we adapted the intramolecular energy transfer (IET) to calculate, for the first time, the energy transfer rates for M–Ln(III) complexes. A new model was proposed that considers the assistance of phonons in the calculation of ET rates. As an example, the proposed model can estimate the ET rates between Eu(III) and Cr(III) ions in the [CrEuL₃]⁶⁺ complex (where L = 2-{6-[N,N-diethylcarboxamido]pyridin-2-yl}-1,1′-dimethyl-5,5′-methylene-2′-(5-methylpyridin-2-yl)bis [1H-benzimidazole]). The calculated rates (930–1200 s⁻¹) are in excellent agreement with the experimentally available data (750–1200 s⁻¹) when a phonon-assisted energy transfer process is considered. Thus, this proposed model can be useful to predict and explain photophysical properties driven by the energy transfer between Ln(III) ions and transition metals. Full article

Nowadays, orthovanadates are studied because of their unique properties for optoelectronic applications. In this work, the LuVO₄:Eu³⁺, Bi³⁺ films were prepared by the sol–gel method, using a new simple route, and deposited by the dip-coating technique. The obtained films are transparent, fracture-free, and homogenous. The sol–gel process was monitored by Fourier-transform infrared spectroscopy (FTIR), and according to X-ray diffraction (XRD) results, the crystal structure was tetragonal, and films that were highly oriented along the (200) low-energy direction were obtained. The morphological studies by scanning electron microscopy (SEM) showed uniformly distributed circular agglomerations of rice-like particles with nanometric sizes. The luminescence properties of the films were analyzed using a fixed concentration of 2.5 at. % Eu³⁺ and different concentrations of Bi³⁺ (0.5, 1.0, and 1.5 at. %); all the samples emit in red, and it has been observed that the light yield of Eu³⁺ is enhanced as the Bi³⁺ content increases when the films are excited at 350 nm, which corresponds to the ¹S₀→³P₁ transition of Bi³⁺. Therefore, a highly efficient energy transfer mechanism between Bi³⁺ and Eu³⁺ has been observed, reaching up to 71%. Finally, it was established that this energy transfer process occurs via a quadrupole–quadrupole interaction. Full article

We report photon–phonon atomic coherence (cascade- and nested-dressing) interaction from the various phase transitions of Eu³⁺: BiPO₄ crystal. Such atomic coherence spectral interaction evolves from out-of-phase fluorescence to in-phase spontaneous four-wave mixing (SFWM) by changing the time gate. The dressing dip switch and three dressing dips of SFWM result from the strong photon–phonon destructive cross- and self-interaction for the hexagonal phase, respectively. More phonon dressing results in the destructive interaction, while less phonon dressing results in the constructive interaction of the atomic coherences. The experimental measurements of the photon–phonon interaction agree with the theoretical simulations. Based on our results, we proposed a model for an optical transistor (as an amplifier and switch). Full article

Rare earth europium(II) complexes based on d-f transition luminescence have characteristics of broad emission spectra, tunable emission colors and short excited state lifetimes, showing great potential in display, lighting and other fields. In this work, four complexes of Eu(II) and bis(pyrazolyl)borate ligands, where pyrazolyl stands for pyrazolyl, 3-methylpyrazolyl, 3,5-dimethylpyrazolyl or 3-trifluoromethylpyrazole, were designed and synthesized. Due to the varied steric hindrance of the ligands, different numbers of solvent molecules (tetrahydrofuran) are participated to saturate the coordination structure. These complexes showed blue-green to yellow emissions with maximum wavelength in the range of 490–560 nm, and short excited state lifetimes of 30–540 ns. Among them, the highest photoluminescence quantum yield can reach 100%. In addition, when the complexes were heated under vacuum or nitrogen atmosphere, they finally transformed into the complexes of Eu(II) and corresponding tri(pyrazolyl)borate ligands and sublimated away. Full article

The smart meta-superconductor MgB₂ and Bi(Pb)SrCaCuO increase the superconducting transition temperature (T_C), but the changes in the transport critical current density (J_C) and Meissner effect are still unknown. Here, we investigated the J_C and Meissner effect of smart meta-superconductor MgB₂ and Bi(Pb)SrCaCuO. The use of the standard four-probe method shows that Y₂O₃:Eu³⁺ and Y₂O₃:Eu³⁺+Ag inhomogeneous phase significantly increase the J_C, and J_C decreases to a minimum value at a higher temperature. The Meissner effect was measured by direct current magnetization. The doping of Y₂O₃:Eu³⁺ and Y₂O₃:Eu³⁺+Ag luminescent inhomogeneous phase causes a Meissner effect of MgB₂ and Bi(Pb)SrCaCuO at a higher temperature, while the non-luminescent dopant reduces the temperature at which samples have Meissner effect. The introduction of luminescent inhomogeneous phase in conventional MgB₂ and copper oxide high-temperature Bi(Pb)SrCaCuO superconductor increases the T_C and J_C, and Meissner effect is exerted at higher temperature. Therefore, smart meta-superconductivity is suitable for conventional and copper oxide high-temperature superconductors. Full article